Guarantees
When shuffling the game, the game runs a "sanity check" to try to insure that the game is beatable (if it's not beatable, it will try again with a different random seed until it works). So as to insure all players are on the same playing field, the following rules are implemented:
The path to find the Bow cannot contain a room in which Gohma must be defeated in order to advance.
The path to find the Recorder cannot contain a room in which Digdogger must be defeated in order to advance.
If playing in Swordless mode, the path to find the Wand cannot contain a room in which a Gleeok or Pol's Voice must be defeated in order to advance.
The path to find the Ladder cannot contain a room which requires you to use a Ladder to advance (specifically, if dungeon rooms are not shuffled, this applies to Level 7 in Quest 1, Level 7 in Quest 2, and the room that normally contains the Magic Key in Level 8 of Quest 2).
The raft, ladder, recorder, and bow, and bracelet will not be in Level 9 (unless "Allow Important Items in 9" is checked).
For Swordless mode, the Wand will not be in Level 9 (unless "Allow Important Items in 9" is checked).
The Raft cannot be on an island that you normally need to use a Raft to enter (original Level 4, or normally the island with the Heart Container)
The Recorder cannot be under the Lake, or in any location opened by the recorder.
Following the above rules, all items must be obtainable.
At least one Blue Candle shop must be located in a shop accessible with items found on the Overworld; specifically, that shop will not be under a bush, on an island, or require the recorder or ladder to access.
At least one Arrow shop will be located in a shop such that it does not require the Raft, Recorder, Bracelet, or Ladder to access.
At least one Bait shop will be located in a shop such that it does not require the Raft, Recorder, Bracelet, or Ladder to access.
If dungeon rooms are shuffled, then there is a guarantee that every room is reachable from the start of the dungeon if the appropriate equipment is held.